linux-kernel - Re: Still OOM problems with 4.9er/4.10er kernels

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Date:   Mon, 27 Feb 2017 10:44:49 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Minchan Kim <minchan@...nel.org>
Cc:     Gerhard Wiesinger <lists@...singer.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: Still OOM problems with 4.9er/4.10er kernels

On Mon 27-02-17 18:02:36, Minchan Kim wrote:
[...]
> >From 9779a1c5d32e2edb64da5cdfcd6f9737b94a247a Mon Sep 17 00:00:00 2001
> From: Minchan Kim <minchan@...nel.org>
> Date: Mon, 27 Feb 2017 17:39:06 +0900
> Subject: [PATCH] mm: use up highatomic before OOM kill
> 
> Not-Yet-Signed-off-by: Minchan Kim <minchan@...nel.org>
> ---
>  mm/page_alloc.c | 14 ++++----------
>  1 file changed, 4 insertions(+), 10 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 614cd0397ce3..e073cca4969e 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3549,16 +3549,6 @@ should_reclaim_retry(gfp_t gfp_mask, unsigned order,
>  		*no_progress_loops = 0;
>  	else
>  		(*no_progress_loops)++;
> -
> -	/*
> -	 * Make sure we converge to OOM if we cannot make any progress
> -	 * several times in the row.
> -	 */
> -	if (*no_progress_loops > MAX_RECLAIM_RETRIES) {
> -		/* Before OOM, exhaust highatomic_reserve */
> -		return unreserve_highatomic_pageblock(ac, true);
> -	}
> -
>  	/*
>  	 * Keep reclaiming pages while there is a chance this will lead
>  	 * somewhere.  If none of the target zones can satisfy our allocation
> @@ -3821,6 +3811,10 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
>  	if (read_mems_allowed_retry(cpuset_mems_cookie))
>  		goto retry_cpuset;
>  
> +	/* Before OOM, exhaust highatomic_reserve */
> +	if (unreserve_highatomic_pageblock(ac, true))
> +		goto retry;
> +

OK, this can help for higher order requests when we do not exhaust all
the retries and fail on compaction but I fail to see how can this help
for order-0 requets which was what happened in this case. I am not
saying this is wrong, though.

>  	/* Reclaim has failed us, start killing things */
>  	page = __alloc_pages_may_oom(gfp_mask, order, ac, &did_some_progress);
>  	if (page)
> -- 
> 2.7.4

-- 
Michal Hocko
SUSE Labs